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With the economy on steroids this year there is tremendous construction activity all over the United States. Washington, DC is no exception and we're seeing constant renewal where outdated buildings are giving way to new construction. This means demolition and foundation work in close proximity to existing structures. Care must be taken and disturbance minimized when working within inches (literally) of existing buildings which are occupied, functioning workplaces or residences.

Rockwheel excavator mounted rock cutting attachments (sometimes called drumcutters or cutterheads) are an ideal tool when both accuracy and productivity must be achieved simultaneously. In this case, a limestone bedrock foundation needed to be deepened immediately adjacent to an adjoining building footer. To avoid the risk of damage to the neighboring structure hydraulic hammers were not an option because of shock waves and vibrations that would be reverberate through the rock mass and concrete. This can result in cracks and unseen microfractures that weaken the foundation.

Rock grinding attachments attack the rock in a very different manner than hydraulic hammers. Unlike hammers (i.e. breakers), which go after the unconfined compressive strength (UCS) of the rock, the shearing action of the rotating conical carbide picks (teeth) exploits the tensile strength of the rock which is 10%-15% of the UCS. By "raking" the rock at 45-50 deg. attack angle an added benefit is creation of smaller rock fragments and these cuttings can often be used onsite as backfill without crushing. This mechanical rock cutting or grinding results in significantly lower seismic disturbance which means safer rock excavation when close to buildings or other sensitive infrastructure such as gas lines. Moreover, the degree of precision of rock or concrete cutting is exceptional. Rapid and Precise are two words frequently used to describe the cutting action of the Rockwheel drum cutters. Compared to other rock grinding attachments on the market the Rockwheel rock and concrete grinders have a optimal layout of teeth on the drums which results in a smooth cutting action. This means less frequent stalling of the cutterhead, more continuous rock cutting and ultimately more CY/hr (m3/hr). For exceptionally hard material when pick penetration is hampered a demolition drum can be used which features a helical depth limiter which prevents the tool from try to take too big of a "bite". This less aggressive drum decreases vibrations and stalling of the cutterhead which means the Rockwheel is cutting rock a greater percentage of the time.

So...the next time you're faced with rock on concrete removal in a sensitive site where collateral damage is unacceptable give the experts at Rockwheel Americas a call. We'll gladly work with your local excavator dealer to ensure optimal hydraulic set up for peak performance of the rock cutting attachment. We have a national rental fleet and gladly work either customer direct or through your local equipment dealer. We maintain an extensive inventory so units can be delivery typically in less than 1-week. Rent, Purchase, or RPO (rental purchase option)...your call. Dealers, we're always looking to building new relationships so call about our demonstration and consignment program. www.alpinecutters.com

The Challenge: Along a vital waterway managed by the USACE (United States Army Corps of Engineers) a customer needed to remove several sections of 4-ft thick x 8-ft high concrete walls. Concrete was unreinforced with a compressive strength of 4000-psi ( 27.5 MPa). Vibrations needed to be kept to a minimum to ensure no disturbance to adjacent structures. Access was limited to an earthen bench about 25-ft away on the opposite side of a cut. Hydraulic hammers would cause too much disturbance via vibrations and shock waves and were not permitted plus they did not have the capability to provided the desired profiled finished surface. How best to remove these ?

The Solution: In consultation with Rockwheel Americas a model D20 Rockwheel (95hp) rock and concrete drum cutter was selected to be installed on a CAT320EL excavator. The Rockwheel was in-stock and ready to go thanks to Rockwheel Americas extensive inventory and national rental fleet. We advised the excavator technician on setting hydraulic flow and pressure for optimal performance. It is always worth the time on the front-end to get the auxilliary hydraulics dialed in so drum speed (rpm) and torque suit the task while making sure multi-functionality on the excavator is not compromised. The Rockwheel installation was "plug and play" thanks to clean hose routing that matches that of the excavator hydraulic lines. No case drain line required and no long hoses crossing the stick.

Performance: The customer was very pleased with the performance and expects to speed up the process as the operator becomes increasingly skilled with the Rockwheel. The high torque Rockwheel rotary drum cutter was the ideal solution. Smooth and continuous concrete grinding was rapid and precise. Moreover, after two 34-yd3 sections of the wall were removed the customer remarked: "teeth wear is virtually zero right now, tips look great after 2 monoliths". High quality carbide conical teeth are always in-stock and can be overnighted anywhere in the country but we recommend keeping a few sets on the job at all times. Clean up was easy thanks to a cutting by-product typically 2" or less in size. Compare this to the blocky remains after hammering which are difficult to haul and dispose.

The base of the cut was smooth and flat, ready for the next phase of the job. It's cliche but its all about "the right tool for the job". Excavator mounted rock and concrete grinders are one of the fastest growing attachments on the market. No longer a tool for mining and underground construction, these are a versatile attachments that should have a place in every serious contractors toolkit. Add one to your arsenal. www.alpinecutters.com Rockwheel is the original rotary cutter...get only the best.

Just last week I was in Hamilton, Ontario, Canada on the western shore of Lake Ontario. Beautiful part of the world. Much of Hamilton is perched on karst topography which involves geological formations with subsurface drainage, caverns and passages caused by dissolving rock, especially prevalent in limestone formations like the Niagara Escarpment. We were at a site where underground infrastructure was being installed for water and sewer services. This means trenching and you didn't have to go very deep until shelf rock was encountered. Where it was permitted the contractor was blasting the rock. Elsewhere hydraulic hammers were in use along with excavator mounted hydraulic rotary drum cutters (i.e. Rockwheels). In some areas of the site, due to the presence of underground karst features, blasting and hammering was explicitly prohibited. In these areas the only option was the Alpine Rockwheel drum cutter. Rockwheels are the lowest vibration method of rock removal. Precise and rapid grinding of the rock limits the disturbance to the surrounding rock mass. A Rockwheel model G40 (200hp) was utilized. Production rates varied depending where we were on the site. Rockwheel rock grinders excel where there are natural fractures and weakness planes but even in the solid rock the rock cutting attachment got the job done. The trench was cut to exact specifications with no overbreak which is a problem with hammers. Cuttings could be reused as backfill saving hauling costs. Rockwheel Americas a division of Alpine has a large inventory of units for rental and purchase. Call 1-814-466-7134 or email info@alpinecutters.com to get more information. You can alwasy find us online at www.alpinecutters.com